Beam sensors are usually used to perform various types of control for improving the running safety of vehicles. Such a beam sensor transmits probing beams, such as laser beams, ultrasonic waves, or millimeter waves, and receives reflected beams, thus detecting targets located around a vehicle.
Such a beam sensor is mounted to a predetermined mount position of a vehicle while the beam axis is aligned with a previously designed axis position such that each probing beam is irradiated within a predetermined irradiation range. For this reason, if any factor causes the mounted position of the beam sensor to be deviated from the predetermined mount position, the beam axis may be deviated from the previously designed axis position. This may result in radar waves being out of the predetermined irradiation range. This may deteriorate the detection accuracy of targets to be detected by the beam sensor, deteriorating the accuracy of the various types of control for improving the running safety of the vehicle.
Note that such axial misalignment of the beam axis relative to a previously designed axis position will also be referred to merely as axial misalignment. In addition, axial misalignment in a vertical plane including the beam axis will be referred to as vertical misalignment, and axial misalignment in a horizontal plane including the beam axis will also be referred to as horizontal misalignment.
In view of these circumstances, technologies are proposed for detecting axial misalignment of beam sensors.
For example, a technology disclosed in patent document 1 detects a vanishing point in accordance with an image captured while a vehicle to which a laser beam sensor is installed is running.
Then, during adjustment of the laser beam axis, i.e. while the vehicle is stopped, the technology detects, based on the detected vanishing point and the transmitting direction of a laser beam, the difference between the transmitting direction of the laser beam and the forward direction of the vehicle, and corrects the transmitting direction of the laser beam accordingly.